We propose to study collagens of low helicity capable of binding to fibronectin in their natural form. The proposal is based on the finding that a high molecular weight, basement membrane collage can be isolated in chemical amounts from cultures of mouse endodermal cells by affinity-chromatography on insolubilized collagen-binding fragments of fibronectin under conditions when triple-helical collagen does not bind to fibronectin. The high affinity for fibronectin and the cell adhesive properties of the non-helical collagen suggest that such variants of collagens have biological significance. To investigate this we will isolate collagen, by fibronectin affinity chromatography and by conventional techniques, from several different lines of normal and malignant cells of endodermal, mesenchymal, and epithelial origin and characterize the fibronectin-binding collagen chemically and immunochemically. The biological function of nonhelical collagen will be investigated by studies on its interaction with other matrix components including fibronectin and proteoglycans and through studies on adhesion of cells to collagen. Affinity of collagen for fibronectin and proteoglycans will be studied using solid phase assays employing radioactive or enzyme-labeled ligands. Cell adhesion properties of collagen will be investigated by measuring cell attachment to substrata containing collagen. The sites and domains in collagen which are responsible for the interactions with other matrix components and with cells will be identified and partially characterized by electrophoresis of intact and proteolytically of chemically digested collagen, transfer of gel bands to nitrocellulose, and "staining" of active peptides on the cellulose with labeled ligands and with cells. The work proposed aims at the further understanding of the structure and function of collagen and its role in the formation of basement membranes and extracellular matrices.